That Grey Square?

So I was in a battle and I accidentally right-clicked an empty tile and the part surrojng it turned gray there was no privateer in the fight but an enemy walked onto that space and all my companions who attacked the guy on that tile did criticals btw I am a musketeer and did not increase criticals so to one of the devs is this a dlitch or is this a tile you mark so you can critical strike thanks?

Hmm. Well, right-clicking on a tile is called "marking." It makes the tile glow for all players on the battle board so you can help communicate strategies and call out targets. This has no other game effect than to act as a visual cue during Multiplayer combat.

Any lucky string of critical hits after marking a tile would simply be coincidence.